Question: Jolie earned $\$205$ for babysitting in one month. She spent $d$ dollars going to a water park with some friends. After going to the water park, Jolie had $\$160$ remaining. Write an equation to describe this situation. How many dollars did Jolie spend at the water park?
Answer: Jolie earned $ 205 {$205} babysitting. She spent an unknown number of dollars, which we're calling ${d}$ dollars at the water park. She had $ 160 {$160} remaining after going to the water park. We can represent the amount of money that Jolie has left after visiting the water park as a difference: ${205} - {d}$ We know that she has $ 160 {$160} remaining. We can set these two expressions equal to describe this situation with an equation: ${205} - {d} = {160}$ Other ways to represent the situation with an equation include: ${160} = {205} - {d}$ or ${205} = d + {160}$. Now we can solve for ${d}$. Add ${d}$ to both sides of the equation then subtract ${160}$ from both sides: $\begin{aligned} {205} -{d} +{d} &= {160}+{d} \\ {205} &= {160}+{d} \\ {205} -{160} &= {160}-{160}+{d} \\ {45} &= d \end{aligned}$ The following equation matches this situation: $205-d=160$ Jolie spent $\$45$ at the water park.